ch15_bkes

Chapter 15 - REFRACTION

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Useful Formulas for Chapter 15:

Index of Refraction
$n=\frac{c}{v}$
$index\ of\ refraction=\frac{speed\ of\light\ in\ vacuum}{speed\ of\ light\ in\ medium}$

Snell's Law
$n_i=(sin \theta_i)=n_r(sing \theta_r)$
$(index\ of\ refraction\ of\ first\ medium) x (sine\ of\ the\ angle\ of\ incidence) = (index\ of\ refraction\ of\ second\ medium) x (sine\ of\ the\ angle\ of\ refraction)$

Thin-lens Equation
$\frac{1}{p}+\frac{1}{q}=\frac{1}{f}$
$\frac{1}{distance\ from\ object\ to\ lens}+\frac{1}{distance\ from\ image\ to\ lens}=\frac{1}{focal\ length}$

Magnification of a Lens
$M=\frac{h'}{h}=-\frac{q}{p}$
$magnification=\frac{image\ height}{object\ height}=-\frac{distance\ from\ image\ to\ lens}{distance\ from\ object\ to\ lens}$

Critical Angle
$sin \theta_c=\frac{n_r}{n_i} when n_i>n_r$
$sine(critical\ angle)=\frac{index\ of\ refraction\ of\ second\ medium}{index\ of\ refraction\ of\ first\ medium}$
only when index of refraction of first medium>index of refraction of second medium

Key Terms for Chapter 15
Refraction - The bending of light as it travels from one medium to another
Index of Refraction - The ratio of the speed of light in a vacuum to its speed in a given transparent medium
Lens - A transparent object that refracts light rays, causing them to converge or diverge to create an image
Converging - A lense where the middle is thicker than either end.
Diverging - A lense whose ends are thicker than the middle of the lense.
Total Internal Reflection - The complete reflection of light at the boundary of two transparent media. This happens when the agnle of incidence is greater than the critical angle.
Critical Angle - The minimum angle of incidence for which total internal reflection occurs
Dispersion - The process of separating polychromatic light into its component wavelengths
Chromatic Aberration - The focusing of different colors of light at different distances behind a lens.

15-1 Refraction

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• Refraction causes images to appear different when the object is viewed through a medium which is not air. This occurs because of the bending of light.
• Bending light occurs when the speed of light changes due to the different medium it travels through.
• The index of refraction for air is 1.00. Other values will be given to you accordingly.
• The greater the index of refraction means that there will be more refraction.
• The index of refraction is calculated based on the materials being in a vacuum. ----

15-2 Thin Lenses

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Symbol	Positive	Negative
p	Object is in front of the lens	Object is in back of the lens
q	Image is in back of the lens	Image is in front of the lens
f	Converging Lens	Diverging Lens

How to Draw a Ray Diagram:

1. A ray that comes in parallel to the principal axis and goes out through the focal point
2. A ray that comes in through the focal point and goes out parallel to the principal axis
3. A ray that goes straight through the center of the lens
4. The image is formed where the rays meet

Note: Ray diagrams for all situations are in the textbook on page 571

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15-3 Optical Phenomena

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• Sometimes when light goes from a higher index of refraction to a lower index of refraction, the effect total internal reflection can happen.
• Even if there is no certaing boundary reflection can occur. Ex: Light passing from warm air to cooler air
• Rayliegh scattering is when the atmosphere scatters the shorter wavelengths of light causing the sky to appear blue.

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Practice Problems

1. An object is 30 m in front of a converging lens and the focal point is 10 m. What is the image distance?
2. Find the critical angle for a water(n=1.333) to air boundary.

Answers:

1. 15 meters
2. 48.6 degrees

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All material on this page has been taken from Mr. Strong's class handouts and the Holt Physics Textbook Chapter 15.
Practice Problem 1 was from page 575 of textbook.
Practice Problem 2 was from page 581 of textbook.